Electric signaling system



EEAZA Nut, h Gm E. F. BATES ELECTRIC SIGNALING SYSTEM Filed Dec. 11, 1942 Jar 1. 16, 1945.

Inventor Attorney Patented'Jan. 16, 1945.

UNITED STATES --YPATENT OFFICE ELECTRIC SIGNALING SYSTEM Ernest Frederick Bates, London, England Application December 11, 1942, Serial No. 468,625

7 i In Great Britain April 30, 1942 3' Claims. (01. 17'7367) This invention relates to electric signaling systems. exclusivelyapplicable to fire alarm and analogous systems in which a pluralityv orst'reet boxesis connected in a single circuit to a central station.

It iswell known to arrange a battery at a central station connected to a closed metallic loop connecting a plurality of substations anda supervisory relay at the central station connected in one leg of the loop, this being known as the closed circuit system. Such a system possesses the considerable advantage that it is under practically continuous test for the purpose of ensur ing that the' line is always in proper workingorder and available for signaling purposes. Contacts at each substation connected in the closed loop are opened and closed for signaling from that substation.

Should, however, the c1osed' loop be broken or connected to earth signaling'is prevented or its reliability diminished. The tie-energisation of the supervisory relay, however, gives an alarm that the loop has been broken and it is well known to arrange that under such conditions one pole of the battery at the central. station shall be connected to earth and the other Pole to the two sides of the loop in parallel. A connection'to earth was provided at each substation completed when signaling was to take place from thatsul station and signaling contacts were arranged in such-earth connection, operated simultaneously with those in the closed loop.

Such an arrangement possessed certain disad-' vantages, particularly since it necessitated changes being made in the connections atthe central station in the event of the loop being'broken, although it was possible to perform these changes automatically. It still remained, however, that when the loop was repaired after being 1 broken the change back to the connections required .for closed loop conditions had to be completed manually. I t In order tocoyercome the. disadvantage -it was proposed on the one hand only to make the connection to earth at a substation if the loop had been broken and automatic means was provided to make such a connection only in that event and then to make it on the correct side of the substation to operate the receiving apparatus at the central station. On the other hand it was proposed to make the connection to earth at a substation through a rectifier similarly poled at each substationl 1 lAlthough either of these measures removed certain disadvantages, neither of them removed The invention is particularly'though not the necessity of altering the connections at the central station to work correctly with complete loop and broken loop conditions respectively. All known closed circuit systems also suffer from the disadvantage that a separate battery must be used to feed each loopcircuit.

It is the object of thepresent invention to provide an electric signaling systemfree from these disadvantages and also such a system that is simple and economical. According to the present invention we provide an electric signaling system comprising a first battery at a central-station connectedto a closed loop connecting a plurality of substations, a supervisory relay connected at the central station in one leg of the loop so as to be normally energi'sed by current in the closed loop, a relay at the central station connected in the other legof the loop, a second battery connected in series aiding to the first battery, one pole of said second battery being connected to the pole of said first battery adjacent to said second relay and the other pole of said second battery being connected to earth, means at each substation for making a connection to earth when signaling from said substation is to take place, and two sets of signaling contacts at each substation operated simultaneously, one set being situated in the closed loop and another set situated between said connection to earth and said closed loop.

prises normally closed contacts SL in the closed loop and normally. closed contacts SE situated either in a connection to earth through normally open contacts KE as in box X or in the closed loop at the-opposite side of the earth connection to contacts SL as in box Y.

In the normal operation of the circuit, the relay A is operated in a current from thebattery AB over the closed loop. Relay B may also be operated by the closed loop current, or if desired maybe shunted out from the closed loop and the shunt removed only if the loop be broken and a street box signals over the leg of the loop in which relay B is connected. A convenient arrangement for this purpose is a rectifier MRB connected in parallel with relay B and poled in such direction as to oifer low resistance to the current in the closed loop. This rectifier may conveniently be a metal rectifier such as the well known selenium rectifier. r

If the handle of either of the boxes Xand Y shown be pulled, contacts KE are closed and thereafter contacts SL and SE open and close simultaneously in accordance with the signal code of the particular box. Relay A responds to the opening and closing of the contacts in a circuit from earth, contacts KE, contacts SE, contacts SL, relay A, battery AB, battery BB. earth. Relay B also responds in a circuit from earth, contacts SE, relay B, battery BB, earth. (If rectifier MRB is provided, relay B first operates in this circult and then responds to the opening and closing of the signaling contacts.) Contacts al and bi cause records to be made, as for example by perforating a paper tape in recorders RBI and REZ.

" Preferably magnets operated by closure of contacts al and bl make perforations on the same paper tape.

If, whilst box X is sending in signals, the handle of a second box Y be pulled, relay A Will continue to respond to signals from box X whilst relay B will respond to signals from box Y. If the second box to commence signaling be situated between box X and relay A, relay B will continue to respond to signals from box X whilst relay A will respond to signals from the second box. boxes may signal concurrently and the codes be correctly received at the central station.

If a break in the closed loop takes place, for example at D, relay A de-energises and at its contacts a2 closes an alarm circuit BK as in known systems. There is, however, no necessity for any rearrangement of the circuits at the central station. Signaling from a street box can take place in the same manner as before a break, relay A or relay B responding according to which side of the break in the box that is signaling.

If the closed loop becomes earthed, as for example at E, a current will flow from battery BB through relay B to the earth at E. As previously stated, it is preferable that relay B should be shunted by a rectifier MRB offering low resistance to the normal loop current from battery AB. This rectifier, however, offers high resistance to the current from battery BB to the earth at E, and thus relay B will no longer be shunted and will energise. By its contacts bl it closes a circuit EA. Delay means consisting of a delay action relay DL are provided in this circuit whereby, when the circuit has been closed for a longer period than occurs during normal signaling from a box, an alarm will be given, as for instance by closing of alarm bell circuit as shown. In this way a separate alarm may be given for a break in the loop and for an earthing of the loop so that the nature of the fault occurring will be indicated at the central station. Signaling from a street box to the central station can take place if the loop is earthed'as the contacts SL or SE of the Thus two box interrupt the earth return circuit through either relay A or relay. B at the central station according to which side of the earth is the box which is signaling.

If a short circuit occurs intermediate of the signaling boxes signaling from a box still takes place from the earth at the box.

Contacts BO may be provided at each box which in known manner are normally closed to short circuit the contacts in the loop but are opened when the mechanism of the box is operated.

The present invention reduces the necessity for the use of the non-interfering succession feature since it permits of two boxes sending signals concurrently without risk of mutilation, or interference.

It should be noted that in known closed loop systems a separate battery such as AB is used for each loop from a central station. This is because if a battery common to a plurality of loops were used, an earth on one loop might interfere with signaling on another loop. With the present invention the battery AB and the battery BB may be common to a plurality of closed loops. The resistances RA and RB may be inserted in a loop to reduce the current drain on the battery AB.

Two boxes X and Y are shown to illustrate two different forms that the sub-stations may take. The two forms are equivalent and all the boxes in a system may be of either type.

What is claimed is:

1. An electric signaling system comprising a first battery at a central station connected to a closed loop connecting a plurality of sub-stations, a supervisory relay connected at the central station in one leg of the loop so as to be normally energized by current in the closed loop, a second relay at the central station connected in the other leg of the loop, a rectifier adapted to offer a lower .resistance connected in shunt to said second relay,

a second battery connected in series aiding to the first battery, one pole of said second battery being connected to the pole of said first battery adjacent to said second relay and the other pole of said second battery being connected to earth,

two sets of signaling contacts at each sub-station operated simultaneously, means at each sub-station for making a connection to earth when signaling from said sub-station, said earth connection being connected relative to the signal contacts to establish a ground through one of the sets of signal contacts in shunt relation to the other of said sets of a sub-station and separately operating recording magnets energized by the closing of the supervisory and second relays respectively.

2. An electric signaling system as claimed in claim 1, in which one of the sets of signaling contacts of a signal box is situated in the connection to earth.

3. An electric signaling system as claimed in claim 1, wherein both sets of signaling contacts of a signal box are in series with the closed loop and wherein the connection to earth is made therebetween.

ERNEST FREDERICK BATES. 

